1. Field of the Invention
The present invention relates to a laminated structure and a method for manufacturing the laminated structure, which is favorably used for automobile interior parts such as a door trim, rear side trim and luggage trim and other interior parts of vehicles, as well as for building materials, wall materials and interior panel in buildings and houses.
2. Description of the Related Art
The construction of the interior parts of an automobile will be described using the door trim as an example with reference to FIGS. 19 and 20.
The door trim 1 is composed of an integrated laminate comprising a surface skin layer 3 having an excellent surface appearance on the surface of a shape-retaining resin core material 2 having rigidity enough for mounting on a chassis.
A polypropylene based resin mixed with talc is used for the resin core material 2. A synthetic resin sheet such as a polyvinyl chloride sheet is used for the surface skin 3 that has intrinsically no shape-retaining property, and elastomer sheets such as TPO (thermoplastic olefin) sheet has been frequently used for the surface skin in recent years considering the effect on the environment and availability for recycling.
A conventional method for molding the door trim 1 will be described hereinafter with reference to FIG. 21. The main parts of the die assembly 4 for molding the door trim 1 comprises an upper die 5 capable of ascending and descending with a predetermined stroke, a stationary lower die 6 paired with the upper die 5, and an injector 7 communicating with the lower die 6.
A cavity 5a for molding the final shape of the door trim 1 is formed in the upper die 5 by closing the upper and lower dies 5 and 6, and a core 6a is provided in the lower die 6. A hoist cylinder 5b is connected to the upper die 5 for ascending and descending movement of the upper die with a predetermined stroke, and a manifold 6b and gate 6c provided at the lower die 6 serve as passageways of a molten resin from the injector 7.
Guide posts 6d are provided at four corners of the lower die 6 for maintaining a proper position of the ascending and descending upper die 5, and guide bushes 5c corresponding to respective guide posts 6d are provided in the upper die 5.
Accordingly, the surface skin 3 is set in the die assembly while the upper and lower dies 5 and 6 are open, and a molten resin M is injected into a cavity between the die assembly from the injector 7 through the manifold 6b and gate 6c after closing the upper and lower dies 5 and 6 with each other, thereby the resin core material 2 is formed into a desired curved shape to integrally mold the surface skin 3 onto the resin core material 2.
While the molten resin M is fed on the molding surface of the core part 6a with the die assembly open in FIG. 21 for the convenience of descriptions, the molded resin M is actually injected into the cavity after closing the upper and lower molds 5 and 6 each other.
However, it has been pointed out in the conventional door trim 1 that the material cost becomes high due to a large projection area of the resin core material 2 with a large weight of the article.
The injection pressure for molding is forced to be high due to the large projection area of the resin core material 2. As a result, the die assembly become expensive since a die structure durable to the high injection pressure is required in addition to a long period of molding cycles for cooling and solidifying a large quantity of the molten resin.
Furthermore, the surface skin 3 becomes poor in sound absorbing ability since an air-impermeable synthetic resin sheet is used as a base, making it impossible to expect the sheet to have a sound absorbing property against the noises generated in the cabin.